Single-walled carbon nanotubes coupled with near-infrared laser for inactivation of bacterial cells.

In this study, single-walled carbon nanotubes (SWCNTs) coupled with near infrared (NIR) laser treatment to enhance SWCNT's antimicrobial activity were studied. Salmonella, agram-negative pathogenic bacteria, was used as a model bacteria in this study. We found that NIR treatment (800 nm, 475 mW, for 20 min) to bacterial suspension with 50 microg/ml SWCNTs reduced the cell growth by approximately 55.5% compared with the cell sample with 50 microg/ml SWCNTs alone. Determined by the plating method, the viable cell number in the SWCNTs-NIR treated samples reduced by 2.2 log, while SWCNTs alone only had 0.7 log reduction. Imaging analysis of bacterial cells with and without NIR treatment correlated well with the growth and viable cell reduction measurement. We also found that the enhancement of SWCNTs' antimicrobial activity by NIR treatment was related to the NIR power, the NIR treatment time, and SWCNTs' concentration. The localized heating of SWCNTs under NIR treatment was the likely mechanism to enhance the antimicrobial efficiency of SWCNTs beyond its intrinsic antimicrobial activity. The results of this study suggested that SWCNTs-NIR treatment has the potential to be an effective antimicrobial method.